As the surface material for car interior such as door, seat, ceiling, headrest, tonneau cover, sun visor or instrument panel, surface material of motorcycle saddle, surface material for pouch or surface material for furniture such as chair or settee, a soft polyvinylchloride sheet is conventionally used. And as the surface material, a leather prepared by forming a soft polyvinylchloride layer on the surface of a sheet substrate such as woven, knitted or non woven fabric or polyolefin foam.
Soft polyvinylchloride has a broad variety in it's hardness. The type of soft polyvinylchloride which is used for the ordinary sheet or film is the polyvinylchloride having hardness which when 30-50 weight parts of plasticizer (diethylhexylphthalate) is blended to 100 parts of polyvinylchloride indicates. And, as the soft polyvinylchloride to be used as the surface material for inner door car interior, the polyvinylchloride having hardness which when 70-100 weight parts of plasticizer is blended to 100 parts of polyvinylchloride indicates, that is, fairly soft type is used.
Recently, in connection with the recycling of the resources, the use of polyolefin resin such as random polyethylene, ethylene-vinylacetate resin, hydrogenated styrene-butadiene rubber, further the use of thermoplastic polyurethane instead of soft type polyvinylchloride is proposed, and the leather which uses these mentioned resins is also proposed.
However, when compared with soft type polyvinylchloride, polyolefin leather has following problems. Namely, the surface is easily injured, does not have adaptability to a high frequency welder and does not have sufficient softness. Still more, polyolefin leather has further problem that because the flame resistance of it is not so good, it is necessary to blend a flame retarding agent such as phosphoric acid type or boric acid type to pass the regulation.
The applicant of the present application already proposed acrylic resin leather possessing an acrylic soft resin layer at least one surface of a substrate as a surface material which has softness, is excellent in resistance for surface injuring and is the material which can be processed by a high frequency welder (JPA2000-349405). This acrylic resin leather is excellent as the synthetic resin leather which can take the place of conventional soft polyvinylchloride leather, however, has a problem that a small injury can easily magnifies is pointed out. That is, when the leather is sewed up by a sewing machine, the seam line is easily magnified or the leather tears from the seam line.
The physical property of thermoplastic polyurethane leather is rubber-like and has strong elasticity, while, has no natural softness caused by retarded elasticity which soft polyvinylchloride has, therefore, the feeling of it is inferior to that of soft polyvinylchloride. Further, for the purpose to obtain good softness, it is necessary to blend a plasticizer by high blending ratio, and the plasticizer blended by large blending ratio causes a problem of transference or bloom. Further the problem of poor calendar processability is also pointed out.
Usually, as the thermoplastic polyurethane leather, the leather prepared by forming a thermoplastic polyurethane layer on a substrate using an intermediate of soft polyurethane foam layer is well known. As the method to form a thermoplastic polyurethane layer on a substrate using an intermediate of soft polyurethane foam layer, various methods can be substantially mentioned. In the case, when a foamed soft polyurethane molded foam is used, the poor adhering power of said foam with a substrate or a thermoplastic polyurethane layer caused by a skin layer which said foam has is recognized as a problem. And, by the method which coats an unfoamed polyurethane layer over the surface of a substrate, and piles up a layer of thermoplastic polyurethane on it, then makes said unfoamed polyurethane layer foam, the uniform product can not be obtained, further, there is a problem that the deterioration of urethane by heating is remarkable.
The object of the present invention is to provide a surface material which can take the place of the conventional surface material which uses soft polyvinylchloride sheet. Namely, the object of the present invention is to provide a sheet shaped surface material of polyurethane resin which is suited for the vacuum forming or blow forming and to provide a method for preparation thereof. Further, the object of the present invention is to provide an urethane resin surface material prepared by laminating a knitted fabric, a woven fabric or soft polyurethane slab foam layer to the reverse surface, which is characterized by having high tearing strength, the seam line is not easily magnified or does not tear from the seam line when sewed up by a sewing machine, having good emboss transcribing feature, having good softness and resistance to surface injuring and can be processed by a high frequency welder, and another object is to provide a method for preparation thereof.